Aristocracy, oligarchy, monarchy, and democracy are old concepts of government which can be traced back to Ancient Greece.
Aristocracy is "rule by the best," and the concept comes from Plato's Republic. Plato argued for an aristocracy of philosopher kings. He thought that philosophers were ideally suited to political leadership. Historically, aristocracies have been based on wealth or land ownership. But other criteria have been used throughout the ages.
Monarchies have often flourished alongside aristocracies. Both have been the targets of revolutionaries, as in eighteenth-century France. Monarchies are ruled by a king or queen. Throughout most of history, the monarchs' powers were absolute. Today, most are constitutional monarchs, and they serve as symbols of the state with few real powers. However, Saudi Arabia is an example of a country where the king still holds great power.
Democracy is "rule by the people" themselves or through their representatives. Today, this is the dominant form of government in the West. However, many believe that their representatives do not always act in the interests of the people they represent. For instance, in the United States, elected representatives often pass legislation that overwhelmingly benefits the affluent classes or corporations. Another problem with modern-day democracy is low voter turnout.
Oligarchy is "rule by the few," and that often means the rich. Many people believe that the United States is now an oligarchy rather than a democracy. Billionaires donate huge sums to candidates and are usually rewarded by the passage of favorable legislation. One way to combat this problem is by public financing of election campaigns.